{"title":"Characterization of isomeric acetyl amino acids and di-acetyl amino acids by LC/MS/MS","authors":"Addipilli Ramunaidu, Pallerla Pavankumar, Nagarjunachary Ragi, Rodda Ramesh, Medicharla V. Jagannatham, Prabhakar Sripadi","doi":"10.1002/jms.4982","DOIUrl":null,"url":null,"abstract":"<p>Acetylation of amino acids is important in the molecular biology and biochemistry because they are part of several metabolic pathways. N-acetyl amino acids can form through degradation of N-acetyl proteins or direct acetylation of amino acids by specific enzymes. Acetylation of α-amino acids can be either on the alpha –NH<sub>2</sub> or on the side-chain functional group, where both the acetyl products are isomeric and can show different biological roles. Theoretically, all proteinogenic α-amino acids are expected to undergo acetylation and they can be a part of metabolome. Thus, it is essential to detect and identify all the possible acetylated products of α-amino acids for untargeted metabolomics studies. In this study, it is aimed to synthesize and characterize all acetylated products of natural α-amino acids. A total of 20 N<sub>α</sub>-acetyl amino acids (<b>1</b>–<b>20</b>), six side-chain acetyl amino acids (<b>21</b>–<b>26</b>), and six diacetyl amino acids (<b>27</b>–<b>32</b>) were synthesized and characterized by liquid chromatography-electrospray ionizationtandem mass spectrometry (LC–ESI–MS/MS). The [M + H]<sup>+</sup> ions of all the acetyl amino acids were subjected to MS/MS experiments to obtain their structural information. Apart from the expected loss of (H<sub>2</sub>O + CO) (immonium ions), most of the acetyl amino acids specifically showed loss of H<sub>2</sub>O and loss of a ketene (C<sub>2</sub>H<sub>2</sub>O) from [M+H]<sup>+</sup> ions. The side-chain acetyl amino acids showed a clear-cut structure specific fragment ions that enabled easy differentiation from their isomeric N<sub>α</sub>-acetyl amino acids. The other isomeric/isobaric acetyl amino acids could also be easily distinguished by their MS/MS spectra. The MS/MS of immonium ions of the acetyl amino acids were also studied, and they included characteristic products reflecting the structures of parent N<sub>α</sub>-acetyl and side-chain acetyl amino acids.</p>","PeriodicalId":16178,"journal":{"name":"Journal of Mass Spectrometry","volume":"58 12","pages":""},"PeriodicalIF":1.9000,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Mass Spectrometry","FirstCategoryId":"92","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1002/jms.4982","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"BIOCHEMICAL RESEARCH METHODS","Score":null,"Total":0}
引用次数: 0
Abstract
Acetylation of amino acids is important in the molecular biology and biochemistry because they are part of several metabolic pathways. N-acetyl amino acids can form through degradation of N-acetyl proteins or direct acetylation of amino acids by specific enzymes. Acetylation of α-amino acids can be either on the alpha –NH2 or on the side-chain functional group, where both the acetyl products are isomeric and can show different biological roles. Theoretically, all proteinogenic α-amino acids are expected to undergo acetylation and they can be a part of metabolome. Thus, it is essential to detect and identify all the possible acetylated products of α-amino acids for untargeted metabolomics studies. In this study, it is aimed to synthesize and characterize all acetylated products of natural α-amino acids. A total of 20 Nα-acetyl amino acids (1–20), six side-chain acetyl amino acids (21–26), and six diacetyl amino acids (27–32) were synthesized and characterized by liquid chromatography-electrospray ionizationtandem mass spectrometry (LC–ESI–MS/MS). The [M + H]+ ions of all the acetyl amino acids were subjected to MS/MS experiments to obtain their structural information. Apart from the expected loss of (H2O + CO) (immonium ions), most of the acetyl amino acids specifically showed loss of H2O and loss of a ketene (C2H2O) from [M+H]+ ions. The side-chain acetyl amino acids showed a clear-cut structure specific fragment ions that enabled easy differentiation from their isomeric Nα-acetyl amino acids. The other isomeric/isobaric acetyl amino acids could also be easily distinguished by their MS/MS spectra. The MS/MS of immonium ions of the acetyl amino acids were also studied, and they included characteristic products reflecting the structures of parent Nα-acetyl and side-chain acetyl amino acids.
期刊介绍:
The Journal of Mass Spectrometry publishes papers on a broad range of topics of interest to scientists working in both fundamental and applied areas involving the study of gaseous ions.
The aim of JMS is to serve the scientific community with information provided and arranged to help senior investigators to better stay abreast of new discoveries and studies in their own field, to make them aware of events and developments in associated fields, and to provide students and newcomers the basic tools with which to learn fundamental and applied aspects of mass spectrometry.